U.S. patent application number 09/839716 was filed with the patent office on 2002-04-25 for polyolefin resin molding composite.
This patent application is currently assigned to Mitsubishi Chemical Foam Plastic Corporation. Invention is credited to Tanaka, Masahiro, Yokoyama, Masaaki.
Application Number | 20020048673 09/839716 |
Document ID | / |
Family ID | 18632192 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020048673 |
Kind Code |
A1 |
Yokoyama, Masaaki ; et
al. |
April 25, 2002 |
Polyolefin resin molding composite
Abstract
A foam layer can be formed at a temperature at which the surface
quality of a surface layer is not deteriorated, and a molding
technique that is excellent in adhesiveness of a foam layer and a
surface layer or/and a base member is developed. For the purpose of
obtaining a resin molding composite, the present invention is
characterized by a polyolefin resin molding composite comprising a
surface layer and a foam layer, or a surface layer, a foam layer,
and a base member, wherein the foam layer comprises a foam layer
produced by fusion bonding thermoplastic expanded resin particles
one another by molding, where the thermoplastic expanded resin
particles comprises a core that is made of a crystalline
thermoplastic resin and is in an expanded state and a polyethylene
resin coat covering the core, and the surface layer comprises a
thermoplastic synthetic resin having a melting point of 5.degree.
C. or more higher than a melting point of polyethylene resin
constituting the coat of the particles.
Inventors: |
Yokoyama, Masaaki;
(Yokkaichi-shi, JP) ; Tanaka, Masahiro;
(Yokkaichi-shi, JP) |
Correspondence
Address: |
LYON & LYON LLP
633 WEST FIFTH STREET
SUITE 4700
LOS ANGELES
CA
90071
US
|
Assignee: |
Mitsubishi Chemical Foam Plastic
Corporation
|
Family ID: |
18632192 |
Appl. No.: |
09/839716 |
Filed: |
April 20, 2001 |
Current U.S.
Class: |
428/319.9 ;
428/313.5 |
Current CPC
Class: |
B32B 5/18 20130101; B32B
3/04 20130101; B32B 27/065 20130101; B32B 27/32 20130101; Y10T
428/249972 20150401; B32B 27/20 20130101; B32B 2605/00 20130101;
B32B 5/20 20130101; Y10T 428/249993 20150401; B32B 2266/0214
20130101; Y10T 428/249976 20150401; Y10T 428/249989 20150401; Y10T
428/249991 20150401; B32B 2323/10 20130101; Y10T 428/249988
20150401; Y10T 428/249992 20150401 |
Class at
Publication: |
428/319.9 ;
428/313.5 |
International
Class: |
B32B 003/26 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 21, 2000 |
JP |
2000-121562 |
Claims
What is claimed is:
1. A polyolefin resin molding composite comprising a surface layer
and a foam layer, or a surface layer, a foam layer, and a base
member, the foam layer being produced by fusion bonding
thermoplastic expanded resin particles one another by molding, the
thermoplastic expanded resin particles comprising a core that is
made of a crystalline thermoplastic resin and is in an expanded
state and a polyethylene resin coat covering the core, and the
surface layer comprising a thermoplastic synthetic resin having a
melting point of 5.degree. C. or more higher than a melting point
of polyethylene resin constituting the coat of the particles.
2. A polyolefin resin molding composite according to claim 1,
wherein the polyethylene resin coat covering the core is in a
substantially non-expanded state.
3. A polyolefin resin molding composite according to claim 2,
wherein the polyethylene resin coat contains an ethylene polymer
having a melting point lower than the crystalline thermoplastic
resin constituting the core, or an ethylene polymer that
substantially exhibits no melting point.
4. A polyolefin resin molding composite according to claim 3,
wherein compressive hardness of the foam layer is 0.05 to 0.7
MPa.
5. A polyolefin resin molding composite according to claim 4,
wherein void fraction of the foam layer is 1 to 40%.
6. A polyolefin resin molding composite according to claim 3,
wherein the thermoplastic synthetic resin constituting surface
layer is a polyolefin resin.
7. A polyolefin resin molding composite according to claim 6,
wherein compressive hardness of the foam layer is 0.05 to 0.7
MPa.
8. A polyolefin resin molding composite according to claim 7,
wherein void fraction of the foam layer is 1 to 40%.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a polyolefin resin molding
composite and, more specifically, to a polyolefin resin molding
composite using thermoplastic expanded resin particles.
[0003] 2. Description of the Related Art
[0004] With respect to a vehicular interior decoration member,
there has hitherto been a member comprising an intervening foam
layer between a base member of a solid resin and a surface layer,
thereby attaching soft touch to the member to make it luxurious.
The process for producing such a vehicular interior decoration
member is disclosed in a patent publication (Pat. No.
2,500,645).
[0005] The process for producing a vehicular interior decoration
member disclosed in the above patent publication comprises placing
a sheet for a surface layer made of polypropylene on one mold, and
on the other mold, placing a base member made of a solid resin that
is made of polypropylene and contains fillers, filling expanded
resin particles made of polypropylene into the space between the
sheet for a surface layer and the base member, thereby fusion
bonded particles one another to form a foam layer. This process
provides such a mold.
[0006] However, the hitherto mold producing technique needs high
temperature or high pressure steam heating when expanded resin
particles are fusion bonded. This leads to a drawback that surface
quality of a surface layer is deteriorated by heat when heating.
Therefore there is another drawback that when a design as an
interior decoration member is formed on the surface of a surface
layer, the design becomes difficult to predominate. There is also
another problem that if molding is carried out at a low
temperature, fusion bonded between expanded resin particles is
deteriorated and adhesion of the surface layer and the foam layer
and of the foam layer and the base member are also
deteriorated.
[0007] Furthermore, the above mentioned hitherto molding composite
producing technique requires to heat for a long time by a high
temperature steam in order to increase adhesiveness between a sheet
for a surface layer and expanded resin particles. Because of this
condition, when fusion bonded by heating is conducted, much
moisture in a gas state infiltrates into spaces between expanded
resin particles or particles themselves. If cooling is carried out
in this condition, moisture condenses from the gas state to the
liquid state, thereby causing great volume shrinkage.
[0008] On this account, pressure in the spaces between expanded
resin particles or in the particles themselves reduces, thereby
causing shrinkage or deformation of an expanded mold made of these
particles. This leads to a problem that shape stability becomes
worse, that it is hard to obtain a mold fitted exactly in a mold,
and that surface appearance of a surface layer is bad. Moreover, in
respect of an expanded mold, it is needed that expanded resin
particles are sufficiently fusion bonded one another, thereby
achieving a high mechanical strength.
[0009] The present inventors have investigated wholeheartedly these
problems of a hitherto molding composite having a foam layer,
thereby developing an excellent molding technique that a foam layer
can be molded at such a temperature as not to deteriorate surface
quality of a surface layer, and a technique excellent in
adhesiveness of a foam layer and a surface layer or/and a base
member, and achieving a resin molding composite.
SUMMARY OF THE INVENTION
[0010] The present invention is a polyolefin resin molding
composite, and is constituted as follows to overcome the above
mentioned technical problems. That is, the present invention is
characterized by a polyolefin resin molding composite comprising a
surface layer and a foam layer, or a surface layer, a foam layer,
and a base member, wherein the foam layer comprises a foam layer
produced by fusion bonding thermoplastic expanded resin particles
one another by molding, where the thermoplastic expanded resin
particles comprises a core that is made of a crystalline
thermoplastic resin and is in an expanded state and a polyethylene
resin coat covering the core, and the surface layer comprises a
thermoplastic synthetic resin having a melting point of 5.degree.
C. or more higher than a melting point of polyethylene resin
constituting the coat of the particles.
[0011] The polyolefin resin molding composite of the present
invention is consisted of the above mentioned required elements,
and is satisfactorily accomplished in the case that the elements
are specifically the following elements. One of the specific
elements is characterized by that thermoplastic synthetic resin
constituting the surface layer is a polyolefin resin. It is also
preferable that compressive hardness of the foam layer is 0.05 to
0.7 MPa. Moreover, it is also preferable that void fraction of the
foam layer is 1 to 40%.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a perspective view of the thermoplastic expanded
resin particles of the foam layer constituting the polyolefin resin
molding composite of the present invention.
[0013] FIG. 2 is a schematic sectional view of the middle of the
process for forming the polyolefin resin molding composite of the
present invention.
[0014] FIG. 3 is a schematic sectional view of the process
following the forming process of the resin molding composite shown
in FIG. 2.
[0015] FIG. 4 is a partial sectional view of an embodiment in which
the polyolefin resin molding composite of the present invention is
applied to a dashboard of a car.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0016] The foam layer constituting the polyolefin resin molding
composite of the present invention uses expanded resin particles
comprising a particular core and a coat covering the core. On that
account, without using high temperature and high pressure steam
that has hitherto been used as a heating medium when an expanded
resin mold is produced, an expanded resin mold can be obtained by
heating with comparatively low temperature and low pressure steam
or hot air of a dry gas.
[0017] The core is usually constituted by a crystalline
thermoplastic resin. Examples of such a crystalline thermoplastic
resin include, for example, polyethylene resins, polypropylene
resins, polybutene resins, polymethylpentene resins, polyester
resins, polyamide resins, fluororesins, crystalline styrene resins
and the like. Of these, a propylene homopolymer, and random
copolymers or block copolymers of propylene with .alpha.-olefin
except propylene are preferable. On this account, a resin molding
composite that is inexpensive, excellent in recyclability, light,
and excellent in insulation and cushioning ability can be
obtained.
[0018] The coat is preferably in the substantially non-expanded
state. "The substantially non-expanded state" means a film state
that has no bubble structure. The film state may have pores, for
example, may be reticulated. Furthermore, the coat contains an
ethylene polymer that has a melting point lower than thermoplastic
resin of the above mentioned core, or that substantially exhibits
no melting point. The melting point of the coat is preferably
15.degree. C. or more lower than the melting point of the
thermoplastic resin constituting the above mentioned core.
Temperature difference between the melting point of the coat and
that of the thermoplastic resin is preferably 20 to 60.degree. C.,
more preferably 20 to 40.degree. C.
[0019] "Substantially exhibit no melting point" means that when
measurement of a melting point by a differential scanning
calorimeter is carried out, no crystalline melting point is
exhibited because of noncrystalline resin. However, such a resin
can be used as a coat since the resin itself is fusion bonded at a
comparatively low temperature. In the case of such a thermoplastic
resin, the temporary melting point is set at 100.degree. C. and
melting point difference between this resin and the crystalline
thermoplastic resin constituting the core is calculated (so is the
melting point difference between this resin and a surface layer
mentioned below).
[0020] Examples of such a low melting point ethylene polymer
include low density polyethylene, linear low density polyethylene,
linear ultra-low density polyethylene as well as copolymers of
ethylene with vinyl acetate, unsaturated carboxylic acid esters,
unsaturated carboxylic acids, vinyl alcohol and the like.
[0021] Examples of an ethylene polymer that substantially exhibits
no melting point include, for example, rubbers and elastomers such
as ethylene/propylene rubber, ethylene/propylene/diene rubber,
ethylene/acrylic rubber, chlorinated polyethylene rubber, and
chlorosulfonated polyethylene rubber.
[0022] These ethylene polymers maybe used singly or as a
composition of two or more kinds of the polymers.
[0023] Of the ethylene polymers constituting the above coat, low
density polyethylene, linear low density polyethylene, and linear
ultra-low density polyethylene are preferable. Of these, linear low
density polyethylene and linear ultra-low density polyethylene that
are polymerized using metallocene catalyst are most preferable.
[0024] The above ethylene polymers constituting the coat has
preferably substantially no melting point or, if any, a melting
point of 125.degree. C. or lower. The reason is because the heating
temperature when expanded resin particles are molded is set at a
lower temperature. Furthermore, concerning the coat, an ethylene
polymer having a melting point of 15.degree. C. or more lower than
that of the thermoplastic resin constituting the core may be
preferably selected and used.
[0025] If the above melting point difference is smaller than
15.degree. C., under the condition that the thermoplastic resin of
the core is expanded, the coat made of the ethylene polymer is also
likely to be expanded.
[0026] The above coat is preferably a mixture of the above ethylene
polymer and crystalline thermoplastic resin that is the same kind
as the core. This leads to improvement of adhesiveness between the
coat and the core.
[0027] The blending content of the thermoplastic resin in the coat
is preferably selected from the range from 1 to 100 parts by weight
for 100 parts by weight of the ethylene polymer. If the blending
content of the thermoplastic resin is smaller than 1 part by
weight, effect of improvement of adhesiveness between the core and
the coat is likely to be worsened. If the blending content exceeds
100 parts by weight, since the sea and island conformation of the
coat changes, thermoplastic resin constitutes a continuous sea
phase. On this account, the heating temperature when molding cannot
be lowered very much.
[0028] Moreover, the blending content of thermoplastic resin is
preferably from 1 to 50 parts by weight for 100 parts by weight of
the ethylene polymer. This improves adhesiveness between the core
and the coat, and the heating temperature when molding can be
lowered.
[0029] In expanded resin particles, thickness of the coat is
preferably from 1 to 150 .mu.m. If thickness of the coat is smaller
than 1 .mu.m, effect of reduction of the heating temperature when
heating is weak. On the other hand, if thickness of the coat
exceeds 150 .mu.m, although the heating temperature can be lowered
when molding, the proportion of the substantially non-expanded
portion in the coat becomes greater, and mechanical strength of a
mold is likely to be lowered for the expanded magnification.
[0030] Furthermore, thickness of the coat is preferably from 10 to
100 .mu.m. On this account, the heating temperature can be reduced
when molding, and mechanical strength of the resin molding
composite can also be improved.
[0031] An expanded resin particle 1 constituting the foam layer of
the polyolefin resin molding composite of the present invention is
shown in FIG. 1. As shown in FIG. 1, L/D ratio, which is a ratio of
a long diameter L and a short diameter D of expanded resin particle
1, is about from 0.5 to 3. If the ratio is smaller than 0.5,
surface area of the coat 3 is diminished, thereby leading to a poor
fusion bonded. If L/D ratio exceeds 3, since particle shape is long
and narrow, filling efficiency is deteriorated, thereby leading to
a poor molding and lowering of shape stability.
[0032] In the case of comparatively greater L/D ratio of 1.5 to 3,
it becomes easy to obtain a mold having many spaces. Concerning
molding performance, L/D ratio is preferably from 0.8 to 2. The
average of the short diameter D of expanded resin particles 1, that
is, average particle diameter is 1 to 6 mm, and preferably 1.5 to
4.0 mm.
[0033] Expanded resin particles 1 can be obtained by, for example,
after impregnating composite particles, as shown in FIG. 1, which
comprises a core 2 made of a crystalline thermoplastic resin and a
coat 3 containing an ethylene polymer that has a lower melting
point than the thermoplastic resin or that exhibits substantially
melting point, with a volatile expanding agent, heating to beno
expanded.
[0034] Examples of the above expanding agent include lower
aliphatic hydrocarbons such as propane, butane, pentane, heptane,
cyclopentane and cyclohexane, halogenated hydrocarbons such as
dichlorodifluoromethane and trichloromonofluoromethane, and
inorganic gases such as nitrogen, air and carbon dioxide. These are
used singly or combined with two or more kinds of the agents.
[0035] Expanded resin particles are molded by steam or hot air. In
the case of hot air, hot air can be obtained by heating air using
heating means such as an electric heater and a steam heater. If hot
air is supplied using a blower or compressed air, expanded resin
particles can be efficiently heated. Furthermore, loss of thermal
energy can be reduced by using a method of recycling and
circulating hot air.
[0036] When using hot air, a dry gas having vapor pressure of 50
KPa or lower is preferably used. On this account, moisture
condenses are not in the spaces between expanded resin particles or
particles themselves when molding, thereby retaining shape
stability of a resin molding composite.
[0037] Molding is carried out at a heating temperature of expanded
resin particles lower than a melting point of a crystalline
thermoplastic resin of a core. A temperature 5.degree. C. or more
lower than the melting point of the above resin is preferable. A
temperature 10.degree. C. or more lower than the melting point of
the above resin is more preferable. Molding is conducted at a
heating temperature higher than a melting point of a coat.
[0038] When molding expanded resin particles, the compression state
of expanded resin particles is appropriately set according to the
physical properties required for a mold. If compression is reduced,
a mold having spaces, in which a contact area of expanded resin
particles themselves is small, can be obtained. In the present
invention, void fraction of a foam layer is preferably from 1% to
40%. Either heating or compression may be carried out earlier.
Compression may be carried out during heating.
[0039] Molding of expanded resin particles is preferably carried
out in the condition that bulk volume of the expanded resin
particles is compressed 50 to 99% to make apparent density higher.
If the compression rate is smaller than 50%, since a resin molding
composite having almost no spaces is obtained, the density of a
resin molding composite becomes too large. If the compression rate
is larger than 99%, since the contact area of expanded resin
particles themselves becomes smaller, a resin molding composite of
which adhesion strength is weak is obtained.
[0040] Compressive hardness of a foam layer is preferably from 0.05
to 0.7 MPa (measured based on JIS K6767), and more preferably from
0.07 to 0.6 MPa.
[0041] If the compressive hardness exceeds 0.7 MPa, expanded resin
particles of the foam layer is hard, and a trace of particles is
likely to be occurred on a surface layer, thereby spoiling surface
appearance and causing a poor cushioning performance. If it is
smaller than 0.05 MPa, expanded resin particles of the foam layer
is soft, and wrinkle is likely to be occurred in a surface layer,
thereby spoiling surface appearance and decreasing strength as an
expanded resin molding composite.
[0042] Expanded resin particles comprises a core that is a closed
wall cell foam made of a crystalline thermoplastic resin, and a
coat that contains an ethylene polymer and is substantially a film
shape. On that account, expanded resin particles can be heated to a
temperature required for fusion bonded of the coat with suppressing
softening of the core that has a higher melting point than the coat
by passing steam or hot air that has a comparatively low heat
capacity through the spaces between expanded resin particles filled
in a mold. Thereafter, a resin molding composite can be obtained by
fusion bonding expanded resin particles using effectively a
compression repulsion that the core has.
[0043] The above mentioned expanded resin particles has a composite
structure that is constituted by a core that is in an expanded
state and a polyethylene resin coat covering the core that is in a
substantially non-expanded state. The core in an expanded state,
for example, has a closed cell structure or an open cell structure,
and a closed cell structure is preferable. The reason is because a
closed cell structure has a high compression repulsion of the core
when molding, and compressive strength is high even at a low
density. Closed cell rate of the core is preferably 50% or higher,
and more preferably 70% or higher. This makes a compression
repulsion of the core when molding further higher, and a resin
molding composite of which compressive strength is high even at a
low density can be obtained.
[0044] With respect to expanded resin particles for use in the
present invention, when the particles are filled in a mold and
fusion bonded using hot air of a comparatively low temperature and
low pressure steam or a dry gas, infiltration of steam into the
spaces between expanded resin particles or particles themselves
when molding is reduced, compared with the case using a high
temperature and high pressure steam. Therefore volume shrinkage of
a mold accompanying with volume shrinkage by condensation of steam
is reduced. On this account, this resin molding composite is
excellent in shape stability. High temperature aging process in
order to recover dimension and shrinkage deformation is not
necessary or is sufficient for a short period of time.
[0045] Furthermore, in the case of molding by a comparatively low
temperature and low pressure steam or a dry gas, a heavy mold tool
that has a structure enough to resist a high steam pressure used
for molding of hitherto expanded resin particles is not necessary,
and consumption of thermal energy is small. If a surface layer made
of a thermoplastic resin and expanded resin particles are molded
together in a mold, poor fusion bonded affected by moisture of
steam is decreased, thereby fusion bonding strongly the surface
layer of a thermoplastic resin and the coat of expanded resin
particles. Accordingly, the resin molding composite of the present
invention has a high strength of fusion bonded, and is excellent in
mechanical strength.
[0046] A surface layer and a base member, which are fusion bonded
and integrated in a laminated shape with a foam layer made of these
expanded resin particles, are placed in advance in a mold for
molding expanded resin particles and laminated, or are laminated by
fusion bonded and the like after expanded resin particles are
molded to be a given shape.
[0047] For the surface layer, a thermoplastic synthetic resin
having a melting point 5.degree. C. or more higher than a melting
point of a polyethylene resin constituting the coat of the
particles (in the case that the polymer substantially exhibits no
melting point, considered as mentioned above) is used in order to
maintain surface characteristics with retaining heat
melt-adhesiveness of expanded resin particles (the coat of expanded
resin particles).
[0048] As specific examples of the resin constituting the surface
layer, polyolefin resins such as polyethylene resins, polypropylene
resins and polyolefin elastomers are preferably used. These
polyolefin resins may be used singly or as a composition of two or
more kinds of the resins. Concerning the surface layer, it is
important that the surface layer comprises a thermoplastic resin
having a melting point 5.degree. C. or more, preferably 10.degree.
C. or more higher than a melting point of the coat of expanded
resin particles.
[0049] A multi-layered surface layer as well as a single layer is
also used. A film shape mold, a sheet shape mold and a mold that is
previously molded to some extent by vacuum molding, compression
molding, slush molding or injection molding are used, and the
thickness thereof is from 0.3 to 5 mm.
[0050] An example of production of the composite of the present
invention is a cast molding. Specifically, a method that is
generally used is as follows. A surface layer is placed in a mold
that can be heated by hot air or steam, and if necessary, on the
other side, a base member made of a comparatively hard synthetic
resin plate. On the back side of the surface layer (between the
surface layer and the base member), expanded resin particles are
filled and heated by hot air or steam, thereby fusion bonding the
expanded resin particles themselves, and expanded resin particles
and the surface layer (and the base member) to be integrated. In
this process, the condition that an uneven pattern such as a grain
pattern and the like of the surface layer is not disappeared or
blurred, or luster of the surface layer is deteriorated even if
heating is carried out at a temperature at which expanded resin
particles themselves are fusion bonded is the above mentioned
melting point difference.
[0051] In respect of molding methods, as shown in FIGS. 2 and 3, a
method that a surface layer is vacuum molded and a foam layer that
was previously molded before the surface layer is solidified is
pressed and fusion bonded to be integrated, or a method that a
surface layer is press-adhered on a foam layer is considered. In
this case, if a grain pattern is formed on a mold tool for vacuum
molding, pattern making on a surface layer can be conducted.
[0052] As a base member made on the other side of a surface layer,
a comparatively hard polyolefin resins are generally used. This
base member is generally used for shape keeping or as a fixation
keeping portion against other things such as a car body and the
like. Since this base member is not exposed outside, it is not
necessary to care about surface patterns and the like of the base
member.
[0053] Concerning materials of the base member, considering its
adhesiveness with a foam, polyolefin resins are preferably
used.
[0054] If a foam, a surface layer and a base member are all
constituted by polyolefin resins, it is preferable because
regeneration can be easily conducted when retrieved things are
crushed and recycled.
[0055] A general molding method is as follows. After expanded resin
particles are filled in a mold in which a surface layer and a base
member is respectively placed, heating is carried out by passing
heated steam or hot air through the spaces between the expanded
resin particles filled in the mold, thereby fusion bonding expanded
resin particles. Subsequently cooling is conducted to be form a
molding composite. Molding composites can also be formed as shown
in FIGS. 2 and 3.
[0056] That is, as shown in FIG. 2, two heating platens 11
containing a heater 11a on the upper and lower sides of a surface
layer 10 are moved to be positioned, and both sides of the
interposing surface layer are heated. After surfaces of the surface
layer 10 are heated to a given temperature, heating platens 11 are
moved back to the former positions, and the surface layer 10 is
placed on a mold for vacuum molding. Subsequently the mold is
evacuated via many holes 13 opening in the mold, thereby adhering
the surface layer 10 to the mold 12.
[0057] Subsequently, as shown in FIG. 3, on a given position of the
surface layer 10 placed, one side of a foam layer 14 made of
expanded resin particles previously formed as explained above is
pressed while a surface of the surface layer 10 is in a soft and
high temperature condition. A base member is previously placed on
the other side of this foam layer 14. Subsequently, another mold is
covered to form a molding composite. Like this, an end molded
product can be formed by placing the previously formed foam layer
14 in the mold on which the surface layer is placed.
[0058] FIG. 4 is a partially sectional view showing a portion of a
mold in section in the case that the polyolefin resin molding
composite of the present invention is applied to molding of a car
dashboard. This dashboard 15 comprises a surface layer 10, a foam
layer 14, and a base member 16 as shown in FIG. 4.
[0059] The surface layer 10 is formed by a sheet made of a
polypropylene resin, and a mat pattern is formed on the surface
there of. This surface layer 10 can be formed by polyethylene
resins, polypropylene resins, or a styrene-butylene-styrene block
copolymer (SEBS). The base member 16 comprises a solid resin
containing fillers and made of polypropylene. The foam layer 14
that is filled between the base member 16 and the surface layer 10
is formed using the above mentioned thermoplastic expanded resin
particles.
[0060] Thus, when the polyolefin resin molding composite of the
present invention is formed as, for example, a dashboard of a car
and the like, even if a mat pattern and such is formed on the
surface of the surface layer 10, since the melting point of the
coat of expanded resin particles constituting the foam layer is
5.degree. C. or more lower than that of the surface layer,
accordingly the pattern of the surface layer is not damaged when
producing a resin molding composite even if heating is carried out
to a temperature at which expanded resin particles themselves are
fusion bonded.
[0061] Since surface appearance of a surface layer becomes good,
cushioning performance becomes also excellent, and a given strength
as a resin molding composite can be obtained by setting compressive
hardness of a foam layer to 0.05 to 0.7 MPa, the polyolefin resin
molding composite of the present invention is particularly
preferable for the application to a vehicle dashboard and the
like.
[EXAMPLES]
[0062] The polyolefin resin molding composite in the present
invention is illustrated in further detail by examples, the present
invention is not limited to the following examples as long as it is
beyond the object.
(Example 1)
[0063] Using a single screw extruder having an inner diameter of 40
mm, an ethylene/propylene random copolymer (melting point
153.degree. C.) of which the ethylene content is 1.5% by weight was
kneaded, and using a single screw extruder having an inner diameter
of 26 mm, a linear low density polyethylene (melting point
100.degree. C.) that is polymerized with a metallocene catalyst
having a density of 0.907 was kneaded. Subsequently,
ethylene/propylene random copolymer was used for a core and linear
low density polyethylene was used for a coat, and a strand was
extruded from a die having a die orifice of a diameter of 1.5
mm.
[0064] After cooling this strand by passing through a water tank,
the strand was cut so as to be 1.2 mg. The cross section of this
composite particle was observed with a phase contrast microscope,
and it was found that linear low density polyethylene of thickness
of 30 .mu.m covered ethylene/propylene random copolymer.
[0065] Next, in a closed vessel, 100 parts by weight of the above
mentioned composite particles, 250 parts by weight of water, 1.0
part by weight of calcium tertiary phosphate having particle
diameters of 0.3 to 0.5 .mu.m, and 0.007 parts by weight of sodium
dodecylbenzenesulfonate was placed. Subsequently, 20 parts by
weight of butane was supplied into the closed vessel with stirring.
After the contents were filled up 62% volume of the vessel,
temperature was elevated for an hour until a temperature of
145.degree. C. was reached and the temperature was maintained for
30 minutes.
[0066] Subsequently, the releasing valve in the bottom of the
closed vessel was opened, and at the same time nitrogen gas was
introduced from outside into a gas phase inside the closed vessel,
thereby maintaining the pressure in the vessel and releasing the
contents under atmospheric pressure to obtain expanded resin
particles. Thus obtained expanded resin particles had an average
bulk density of 17 Kg/m.sup.3 and an average cell diameter of 230
.mu.m. and there was no blocking of the expanded resin particles
themselves.
[0067] The cross section of this expanded resin particle was
observed with a phase contrast microscope, and it was found that
ethylene/propylene random copolymer of the core was in a closed
cell expanded state, and on the other hand, linear low density
polyethylene was in a substantially non-expanded film state and
covered the expanded state core of ethylene/propylene random
copolymer. L/D, a ratio of a long diameter L and a short diameter D
of an expanded resin particle was 0.9.
[0068] These expanded resin particles was fully dried in a drying
room at 40.degree. C. After these expanded resin particles were
filled in a mold with core vents, or drill holes in which a surface
layer (material: a polypropylene resin sheet, thickness: 0.8 mm,
melting point: 153.degree. C.) and a base member (material: a
polypropylene resin, thickness: 4 mm, melting point: 164.degree.
C.) were respectively placed, surface temperature of expanded resin
particles was heated to 120.degree. C. by passing hot air through
the spaces between expanded resin particles filled in the mold.
Subsequently, in the condition that the volume in the mold was
diminished to 60%, expanded resin particles were fusion bonded.
After that, the product was cooled by air, and a molding composite
was taken out from inside the mold.
[0069] The density of the foam layer was 28 Kg/m.sup.3, the size of
the mold was 200 mm in length, 300 mm in width, and 40 mm in
thickness. There was no water content. The shape was just the same
as the mold without shrinkage and deformation.
(Examples 2 to 6
[0070] Comparative Examples 1 and 2)
[0071] With respect to Examples 2 to 6 and Comparative Examples 1
and 2, as shown in Table 1, expanded molds were produced with
changing the resin and state of the core, the resin and state of
the coat, average bulk density, L/D ratio, the resin and state of
the surface layer, molding temperature, and compression ratio.
Except this, production was carried out in the same manner as in
Example 1.
1 TABLE 1 Compara- Compara- tive tive Example Example Example
Example Example Example Example Example 1 2 3 4 5 6 1 2 The resin
of ET-PR ET-PR ET-PR ET-PR ET-PR ET-PR ET-PR ET-PR the core Melting
153 153 141 141 153 153 153 153 point (.degree. C.) The resin of M-
M- LLDPE LLDPE M- LLDPE ET-PR -- the coat LLDPE LLDPE LLDPE Melting
100 100 123 123 100 123 142 point (.degree. C.) Average 17 18 17 18
17 18 18 18 bulk density (Kg/m.sup.3) L/D ratio 0.9 2.0 1.2 1.5 0.9
1.4 1.3 1.1 The state of Expanded Expanded Expanded Expanded
Expanded Expanded Expanded Expanded the core The state of Substan-
Substan- Substan- Substan- Substan- Substan- Expanded -- the coat
tially tially tially tially tially tially non- non- non- non- non-
non- expanded expanded expanded expanded expanded expanded The
resin of ET-PR ET-PR HDPE HDPE HDPE HDPE ET-PR HDPE the surface
layer Melting 153 153 131 135 131 135 153 135 point (.degree. C.)
Heat 120 125 125 128 115 128 130 125 molding temperature (.degree.
C.) Compression 40 10 30 3 40 10 30 30 ratio (%) The foam 28 20 24
18.5 28 20 Not Not layer Bulk fusion fusion density bonded bonded
(Kg/m.sup.3) Void 1< 30 10 35 1< 30 Measure- Measure-
fraction ment ment impossible impossible Fusion .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. X X bonded test
[0072] ET-PR: ethylene-propylene random copolymer
[0073] M-LLDPE: linear low density polyethylene polymerized with a
metallocene catalyst
[0074] LLDPE: linear low density polyethylene
[0075] HDPE: high density polyethylene
[0076] O: The foam layer is adhered and integrated with the surface
layer, and there is no appearance abnormality such as shrinkage and
deformation.
[0077] X: The form layer is separated from the surface layer, or
there is deformation, shrinkage or the like in the surface
layer.
[0078] The physical properties in the above Examples 1 to 6 and
Comparative Examples 1 and 2 were measured by the following
methods.
[0079] <Melting Point>
[0080] Melting point was measured by a differential scanning
calorimeter (DSC). First, 3 to 5 mg of a resin was heated until a
temperature at which the crystal is melted was reached, then the
resin was cooled down to room temperature at a rate of 10.degree.
C. per minute. Next, the resin was heated at a rate of 10.degree.
C. per minute, and thereby determining a melting temperature as a
peak temperature of the endothermic curve thus obtained.
[0081] <Bulk density of the Foam Layer>
[0082] A foam layer was cut out of the end mold, and the weight per
unit volume (Kg/m.sup.3) was measured.
[0083] <Compression Ratio of the Foam Layer>
(bulk density of the foam layer-bulk density of expanded resin
particles)/(bulk density of the foam layer).times.100(%) (1)
[0084] <Void Fraction>
[0085] In a graduated cylinder having an inner diameter of 150 mm
and a volume of 5 liter, 3 liter of water was placed, and a testing
block of the foam layer having a dimension of
100.times.100.times.30 mm (volume 0.3 liter) was submerged. Then
the volume V (liter) shown by water level was measured, and void
fraction was calculated by formula (2).
{1-(V-3)/0.3}.times.100% (2)
[0086] <Fusion of the surface layer>
[0087] The molding composite taken out of inside the mold was
allowed to stand at a temperature of 20.degree. C., the appearance
after 30 minutes was visually evaluated.
[0088] Although the above mentioned embodiment of the present
invention is explained by an example of a dashboard of a car and
such, the present invention is not limited to such a use, and can
be naturally applied to interior decoration members requiring
cushioning performance, heat insulating performance, or sound
insulating performance, such as a heat insulating panel, or
furniture such as a chair and a desk.
[0089] As explained above, according to the polyolefin resin
molding composite of the present invention, a foam layer can be
formed at a temperature at which the surface quality of a surface
layer is not deteriorated, and a resin molding composite that is
excellent in adhesiveness of a foam layer and a surface layer
or/and a base member can be obtained.
[0090] Moreover, according to the polyolefin resin molding
composite of the present invention, since the melting point of a
coat in thermoplastic resin expanded particles is set to a lower
temperature than the melting point of a surface layer, appearance
of the surface layer is not damaged. Furthermore, since there are
spaces in a foam layer, the polyolefin resin molding composite has
a sound absorbing effect. The thickness of a molding composite can
be further thinned since average particle diameter of expanded
resin particles is small. Thus, excellent effects are achieved
according to the present invention.
* * * * *